Zirconia subbed photographic paper



United States Patent No Drawing. Filed July 29, 1960, Ser. No. 46,057

. 6 Claims. oi. sa -s This invention relates to photographic paper, particularly photographic paper having a layer of a hydrophobic polymeric material such as polyethylene or the like.

Photographic paper is normally composed of a paper support of high purity having thereon a high pigment coating such as barium sulfate over which is coated a lightsensitive silver halide emulsion. For various purposes, other types of photographic paper are needed which are highly resistant to chemical action, require a high degree of dimensional stability, or must Withstand high temperatures involved in certain types of rapid processing. In order to improve photographic papers, waterproof coatings are applied on one or both surfaces in order to limit the penetration of processing chemicals into the absorbed base.

However, many of the waterproof coatings have been hydrophobic in nature so that photographic emulsions have been made to adhere only after some type of surface preparation. In some instances, the polymeric coatings have been made adherent by electron bombardment, chlorination, and oxidation such as flaming, or the like. It has also been necessary to apply a subcoating in addition to the surface treatment to improve the adhesion of photographic emulsions, due to the strenuous conditions which are experienced during photographic processing when the photographic print is immersed in processing liquids, agitated to thoroughly contact the emulsion with the processing chemicals and then subjected to squeegeeing and drying operations.

Photographic emulsions are well known for their sensitivity to various chemical agents. This requires a high degree of care in selecting subbing materials to obtain adhesion to various substrates, and further limits the materials which may be employed to improve the adhesion to polymeric coatings. It has been desired to find a relatively inexpensive method of coating or treating polymeric sur-. faces such as polyethylene or the like which would be compatible with photographic emulsions and which would obtain adhesion suflicient to withstand the vigorous conditions which occur during processing.

I have found a method of coating polymeric substrates such as polyolefins with zirconia to obtain adhesion for photographic emulsions.

One object of this invention is to provide a photographic paper having good adhesion to photographic emulsions. Another object is to provide a method for coating substrates such as paper, paper extruded with polyethylene and polyethylene, and the like, to provide good adhesion to protographic emulsions. An additional object is to provide a sizing for photographic paper which is compatible with photographic emulsions. Anothed object is to provide a sizing which has an acidic pH of 3-3.4 for photographic paper.

The above objects are obtained by coating a substrate with an aqueous dispersion of colloidal zirconia. The colloidal zirconia may be applied to the paper base or to a paper base which has already been sized using other conventional penetration-restricting sizes or pigmented coatings. The size may be applied as a tub size or may be applied on the surface of the substrate using any wellknown method such as knife, bar, wick, kiss-roll, air knife, hopper, or the like. The paper base may be sized previously using an internal size or using a tub size.

. Colloidal zirconia may also be used to sub polymeric surfaces such as polyolefins, polyesters, polycarbonates, cellulose derivatives, polyvinyl resins, polystyrene, and the like. The surface may be coated with colloidal zirconia to obtain adhesion of other coatings such as printing employing various types of ink, decorative designs, and the like. Various coverages of colloidal zirconia may be used depending on the substrate, the coating to be 'a 'p'pliedover" the coating of the zirconia and the like. However, our preferred embodiment is 2-3 g./sq. in. solids basis of colloidal zirconia. For purposes other than photographic emulsions, as little as one gram per square meter may be used. Coverages higher than 3 g./sq. m. may be used, in some instances, as much as 5 g./sq. m. However, with a polymeric substrate such as polyethylene, higher'coverages may result in flaking of the zirconia from the base. The concentration of the zirconia in the water may vary from 5 to 25% based on the total weight of the aqueous dispersion. A wetting agent is desirable such as an alkyl aryl polyether alcohol. The particular wetting agent is not critical but, in the event that a photographic emulsion is to be coated over the zirconia, should be one that is compatible with photographic emulsions. Both nonionic and cationic wetting agents may be used.

The colloidal zirconia described herein may be prepared by reacting zirconyl chloride with an aqueous solution of ammonium carbonate as described in US.

2,467,089 to form a homogeneous hydrosol, or by other known methods. v

. The following examples are intended to illustrate our invention but not to limit it in any way.

Example. 1

A 21 lb./ 1000 sq. ft. paper stock is coated with an extrusion of polyethylene of 0.4 mil thickness 'on both sides of the paper. The untreated polyethylene c'oated paper'is then surface sized with 2 g./ sq. in. solids basis of colloidal zirconia having a concentration in water of 25%, and the coated paper dried with impinged hot air at 70-150 F The sizing solution has the following composition:

Dry Total Weight, Weight, parts parts 25% Colloidal zirconia 10 40 10% Wetting agent (alkyl aryl polyether alcohol). V v 0. 6 6 Water 54 A photographic emulsion as follows is coated over the subbed surface which has been rendered hydrophilic by colloidal zirconia.

I Fine grain silver chloride emulsion containing 1 mole of Ag per 43500 cc g 43.5

Paraflin dispersion prepared as follows: g. molten parafiin dispersed in 400 cc. 10% photographic Water cc 20.0

,Withcolloidal zirconia.

The emulsion is coated on the rate of 6.5 grams per square foot on the base and dried. Very good emulsion adhesion is found during or after processing on this 3 product.

Example 2 The same process is employed as in Example 1 except that the following proportions are used:

Dry Total Weight, Weight, 7

parts parts 25% houses zimdins 1 Q s. 57 34. 2s Aluminumchloride (50% solution in water) 1. 43 2. 86 10% Wetting agent (alkyl aryl polyether alcohol); 0. 6 6. Water 1 p 56. 86

The emulsion is found to be satisfactory. i Example 3 A 21 lb./ 1000 sq. ft. paper stock is coated with 21 gjsq. m. of baryta (barium sulfate). The barytacoated paper is dried and calendercd. Three grams per square meter of colloidal zirconia having a concentration of 25 having the following composition is then coated over the baryta surface: 1

1 Dry Total Weight, Wgight,

parts parts 25% Colloidal zirconia 15- 60 10% Wetting agent (alkyl aryl polyether alcohol) 0. 1 1 Wa r- 39 The zirconia treated surface is then sensitized'with a direct-positivegelatino silver halide emulsion. A significant improvement of emulsion adhesion is I noted when compared with a similar sample which has not been sized For some purposes colloidal zinc oxidemay be used as disclosedherein in place of zirconia.

. The invention has been described in detail with partic ensitive, silver halide-gelatin emulsion to said base on said polymeric film base and a light-sensitive silver halide 2. A sensitized photographic elementcomprisiug a hydrophobic polyolefin base, an adherent coating comprissufficient to increase the adhesion of a light-sensitive,

silver halide-gelatin emulsion to said base on said polyolefin base and a light-sensitive silver halide gelatin emulsion over said adherent zirconia coating. p

3. A sensitized photographic element comprising a hydrophobic. polyethylene base, an adherent coating comprising as the sole adhesive colloidal zirconia in an amount sufiicient' to increase the adhesion of a light-sensitive, sils ver halide-gelatinv emulsion to said base on sm'd polyethylene base and a light-sensitive silver halide gelatin emulsion over said adherent zirconia coating.

4. A sensitized photographic element comprising a paper supported hydrophobicpolyolefin base, an adherent coating comprising as thesole adhesive colloidal zirconia in an amount sufficient to increase the adhesion of a light- 7 sensitive, silver halide-gelatin emulsion to said base on said hydrophobic polyolefin base and a light-sensitive silver halide gelatin emulsion over said adherent zirconia coating. 7

5Q A sensitized photographic element comprising a paper supported hydrophobic polyethylene base, an adherent coating comprising as the sole adhesive colloidal zirconia in an amount suflicient to increase the adhesion of a light-sensitive, silver halide-gelatin emulsion to said base on said hydrophobic polyethylene base and a light- 7 sensitive silver halide gelatin emulsion over said adherent zirconia coating. 6

6. A sensitized photographic element comprising a paper supported hydrophobic polyethylene base, an adherent coating comprising as the sole adhesive 2 to 3 grams per square meter of colloidal zirconia on said hydrophobic polyethylene base and a light-sensitive silver halide gelatin emulsion over said adherent zirconia coating. 1 a 1 References Cited by the Examiner, UNITED STATES PATENTS NORMAN G. TORCHIN, Primary Examiner.

PlilLIP E. MANGAN, H nopp BURSTEIN,

' I Examiners. 

1. A SENSITIZED PHOTOGRAPHIC ELEMENT COMPRISING A HYDROPHOBIC ORGANIC POLYMERIC FILM BASE, AN ADHERENT COATING COMPRISING AS THE SOLE ADHESIVE COLLOIDAL ZIRCONIA IN AN AMOUNT SUFFCIENT TO INCREASE THE ADHESION OF A LIGHTSENSITIVE, SILVER HALIDE-GELATIN EMULSION TO SAID BASE ON SAID POLYMERIC FILM BASE AND A LIGHT-SENSITIVE SILVER HALIDE GELATIN EMULSION OVER SAID ADHERENT ZIRCONIA COATING. 